An exemplary spring operating mechanism used in a gas circuit breaker (abbreviated below as a gas circuit breaker sometimes) that is provided in a substation or switching station and used at voltages of 300 kV or lower is described in Japanese Patent Laid-Open No. 2001-266719. The gas circuit breaker described in this document uses helical springs as a driving source for opening and closing. Another example of a gas circuit breaker is described in Japanese Patent Laid-Open No. Hei 04 (1992)-71131. In the gas circuit breaker described in this document, to make an operation unit compact and achieve high-speed operation, a swinging lever linked to an operating apparatus is provided on a plane parallel to the operation shaft of a movable electrode part. An end of the swinging lever is linked to a driving rod for driving the movable electrode part through at least one floating lever. When a rotational operation angle of the swinging lever is divided into two parts by a line that passes through the rotational center of the swinging lever and is orthogonal to the operation shaft of the movable electrode part, the following relation holds:θ1≧1.5θ2 
where θ1 is a rotational operation angle on the movable electrode part side and θ2 is the remaining rotational operation angle.